Systems for cooling or otherwise controlling the environment are well known. In particular, air conditioners are widely used and operate by drawing in hot air and expelling, into a closed environment, cool dry air.
A disadvantage of air conditioners is that although they effectively cool the air in a closed environment to a comfortable temperature, they also substantially reduce the moisture content of the air and, as a result, persons exposed to the relatively dry air may suffer from sore throats, headaches and related conditions. Furthermore, air conditioners are generally expensive to manufacture and run.
Distinct from air conditioners are evaporative coolers, which are most effective in hot, dry climates. Evaporative coolers, also known as desert coolers, are operative to draw in dry air, to raise significantly its moisture content and to resupply the moist air into the environment. As the air is drawn into the cooler its moisture content is raised and its temperature falls.
Disclosed in U.S. Pats. Nos. 2,187,019 and 2,396,024, are two kinds of evaporative air cooler, both of which include an air blower that is operative to draw air through a water absorbent pad and to expel moist, cooled air into the environment.
Further disclosed, in U.S. Pat. No. 4,231,975 is an evaporative cooler and a water absorbent pad therefor. The pad consists of loosely packed, randomly oriented fibers coated with a thin layer of Portland cement that is water absorbent and that has a granular surface.
The U.S. Patents referred to above disclose coolers in which a blower is provided downstream of the water absorbent pad or in the `wet zone`. The blower is, therefore, exposed to very moist air, together with various maintenance problems that may be caused thereby.
U.S. Pat. No. 2,164,763 relates to a portable air conditioner in which a fan blows air from a dry zone across cloths that are partly submerged in a water tank.
Disclosed in U.S. Pat. No. 2,104,209 is an air conditioner in which a fan blows air through a screen of wick material which is partially immersed in water, water being drawn into the screen by capillary action. The air follows a circuitous route through a baffle configuration.
U.S. Pat. No. 1,991,581 discloses apparatus in which air is drawn through a fabric partially immersed in water.
Disclosed in U.S. Pat. No. 2,464,766 is air conditioning apparatus having a circular evaporative pad which is rotated through a trough of water. The evaporative pad comprises aluminum and wool.
Each of the absorbent pads, wicks or cloths disclosed in the above-referenced U.S. Patents constitutes a medium that is highly water absorbent but from which it is difficult to remove water by application of a pressure gradient thereacross, such as by an air blower. Consequently, a relatively strong air current is required to be provided across the absorbent pads in order for the water retained thereby to be released into the atmosphere.
U.S. Pat. No. 2,342,842 relates to an air conditioning and cooling system including a thermostat and operative to cool air by means of a water spray, the air passing through a filter. This cooling system, it will be appreciated, is inherently wasteful of water.
Available on the market is an air conditioning system intended for use in a computer room. In addition to the need to dissipate heat produced by computers, there is also a need to humidify the environment of a computer room. Marketed by The Hiross Group of, inter alia, the U.S.A. and the U.K. is an air conditioner for computer rooms called MINIOVER. This product includes a cooling element through which air is passed and cooled, there also being provided a heating element for supplying steam to the cooled on exiting the air conditioner. A disadvantage of this product is its use of a heating element, which consumes energy at a relatively high rate.